Purpose:
Short-term enhancement of visual field (VF) sensitivity after surgical reduction of intraocular pressure (IOP) in glaucomatous eyes has been reported. The purpose of the present study was to examine the hypothesis that long-term VF enhancement occurs in glaucomatous eyes undergoing IOP-lowering surgery.

Methods:
Patients with uncontrolled IOP requiring trabeculectomy or aqueous drainage device implantation were enrolled. Controls consisted of medically treated glaucoma patients with stable IOP. Two baseline preoperative VFs and 3 follow-up VF exams at 12, 24, and 36 months postoperatively were used for analysis. The same number of VF examinations was used for control eyes. VF locations with significant change were defined as exceeding 95% test-retest confidence limits based upon the mean sensitivity using the 2 baseline VF exams. The number of significantly changing locations per eye from the mean baseline fields were compared between groups using a Poisson generalized estimating equation model.

Results:
Twenty eyes (baseline MD -7.0±5.0 dB) of 20 surgically treated glaucoma patients (mean age 69.2±10.1 years) and 41 eyes (baseline MD -5.6±4.2 dB) of 28 controls (mean age 67.4±7.3 years) were enrolled. Mean postoperative IOP (10.83±6.45 mmHg) was significantly (p=0.03) decreased at 3 years of follow-up compared with baseline (17.1±6.32 mmHg) in the surgical eyes, but was similar (p=0.72) in control eyes (13.4±6.46 and 13.7±3.14 mmHg). At 3 years of follow-up, the mean number of test locations with improving VF sensitivity was similar between the surgical and control group in central (0.45±0.89 vs. 0.77±1.13, p=0.273), peripheral (2.10±2.88 vs. 1.92±3.37, p=0.829) and all VF test locations (2.55±3.43 vs. 2.69±4.09, p=0.886). The mean number of test locations with decreasing VF sensitivity was similar between the surgical and control group in central (1.35±2.01 vs. 1.18±1.90, p=0.743), peripheral (3.10±3.88 vs. 3.33±3.88, p=0.825) and all test locations (4.45±5.58 vs. 4.51±5.41, p=0.966).

Conclusions:
VF loss and improvement were comparable through 3 years of post-operative follow-up. This suggests that ongoing glaucomatous damage may erode early postoperative enhancement of VF sensitivity after IOP-lowering surgery.